Why are these sociopathic displays only found on pick-up trucks? Don't other vehicles have back windows? There is plenty of glass on the back of a Prius, for instance.
Patriarchy has its roots in insecurity. To me it seems to be a strain in our culture that revolves around countering its inner fears by projecting menace and the ability and willingness to degrade and instill fear in others.
How safe would you feel around a dirt ball who thinks this window decal is funny? Who wants to be this guy's girlfriend? Who is desperate enough to bear that clod's child and what chance is there that child would be raised with out absorbing the lesson, as children do when steeped in bluster about bravely cavalier treatment of others, that he too should feel unsafe? Its not a joke unless everyone can laugh about it.
I can not think of an easy way out of a self propagating miasma like that. A solution matched to our sick era would be to stimulate the economy by giving these clueless souls large sums of money that can only be spent on psychotherapy. Cheaper I suppose would be to look into my own heart until I found a way to only feel how lost they are and then address them directly without any of my own fear or even reproach.
We all have a long way to go.